I use the cheap rivet setter from knifekits: http://www.knifekits.com/vcom/product_info.php?cPath=41_57&products_id=1564

The dies and arbor press is much more efficient, but you can make the hand setter one work. I've made sheaths for everything from little pikals to Wakis.

You have to try and get the rivet setter as flat as possible, sometimes you think it's straight but it isn't. Tap lightly at first straight down or in a 360 degree motion so that the rivet starts to flare evenly. Once the edge is all facing the right direction, pound on it harder until it seals the kydex. Some days it's just easier than others...